The present invention generally relates to processes for preparing polymeric materials using carbon dioxide and polymeric materials formed thereby.
The formation of well-ordered mesopores in a bulk material is desirable for many applications including separations, anisotropic transport, high surface area catalytic monoliths, and others. Block and graft copolymers may form micro-phase separated morphologies such as spheres, cylinders and lamellas, which can be used to control the orientation of nanostructures of large areas.
Rockford, L. et al., Macromolecules, 34: 1487 (2001) propose films of symmetric diblock copolymers of poly(styrene-block-methyl methacrylate) solution cast onto silicon oxide substrates striped with periodic, 20 nm wide gold lines believed to show lamellar microdomain orientation perpendicular to the substrate plane and parallel to the striping.
Zalutsky, A. S. et al., J. A. Chem. Soc., 123: 1519-1520 (2001) propose a method for the formation of a mesoporous polystyrene monolith thought to contain close-packed aligned nanochannels. This method entails the preparation of diblock copolymers containing oriented nanoscopic cylinders of degradable polylactide embedded in polystyrene followed by selective removal of polylactide using an aqueous methanol mixture containing sodium hydroxide.
In another method, Chan, V. Z.-H. et al, Science, 286: 1716 (1999) propose producing porous and relief ceramic nanostructures from self-assembling (template-free) block copolymer precursors comprising silicon-containing triblock copolymer films, with a one-step, low-temperature technique.
It has been proposed that polymers possessing a low dielectric constant may serve as insulators for microelectronic devices. See Maier, G. et al. Prog. Polym. Sci. 26: 3-65 (2001).
Dang, T. D. et al., J. Polym. Sci. A: Polym. Chem. 38: 1991-2003 (2000) propose the synthesis and characterization of fluorinated benzoxazole polymers. The reference proposes incorporation of perfluoroisopropyl groups along the polymer backbone to contribute to lowered dielectric properties, and that an increase in the number of fused rings along the backbone structure may increase the glass-transition temperature (Tg).
Rajagopal A. et al., J. Vac. Sci. Technol. B, 17(5): 2336-2340 (1999) couples x-ray photoelectron spectroscopy with in situ sample annealing and copper thermal evaporation to study the stability of SiLK(trademark) surface and the physico-chemical interactions at the metal-polymer interface. The reference proposes that upon anneal, copper may tend not to diffuse into the SiLK(trademark) semiconductor dielectric but to coalesce in larger clusters on the resin.
Hedrick, J. L et al., Reactive and Functional Polymers, 30: 43-53 (1996) propose the use of phase separated block copolymers comprised of a high thermally stable Tg polymer and a second component, which can undergo clean thermal decomposition with the evolution of volatile by-products to form what may be a closed-cell porous structure.
There is a need in the art for improved methods of forming polymeric structures and a need in the art for improved polymeric structures.
Methods according to embodiments of the present invention provide polymeric structures that possess beneficial dielectric and/or physical (e.g., size, cell size, cell type, cell density, etc.) characteristics. Such polymeric structures may be advantageously employed in a variety of ways. For example, such polymeric structures may be utilized in microelectronic devices. Advances in microelectronics have resulted in the need for smaller components and, thus, smaller microelectronic devices. As these devices become smaller, the distance between the electrically conducting interconnect lines decreases resulting in an increase in inductive and capacitive effects. Polymeric structures according to embodiments of the present invention having beneficial dielectric and/or physical characteristics may be utilized as dielectric materials in such smaller microelectronic devices.
According to other embodiments of the present invention, methods of forming a polymeric structure having a plurality of cells therein include contacting a polymeric material that includes a first phase that comprises a first polymer, and a second phase that comprises a second polymer, with a composition comprising carbon dioxide and a chemical decomposition agent to remove the second polymer from the polymeric material to form the polymeric structure having a plurality of cells therein.
According to still other embodiments of the present invention, methods of forming a polymeric structure having a plurality of cells therein where the plurality of cells have an average diameter of from about 1 to 25 nm are provided. The methods include contacting a polymeric material that includes a first phase that comprises a first polymer, and a second phase that comprises a second polymer, with a composition comprising carbon dioxide to remove the second polymer from the polymeric material to form the polymeric structure having a plurality of cells therein where the plurality of cells have an average diameter of from about 1 to 25 nm.
According to yet other embodiments of the present invention, methods of forming a polymeric structure having a plurality of cells therein where the polymeric structure has a dielectric constant of from about 1.5 to 3.5 are provided. The methods include contacting a polymeric material including a first phase that comprises a first polymer, and a second phase that comprises a second polymer, with a composition comprising carbon dioxide to remove the second polymer from the polymeric material to form the polymeric structure having a plurality of cells therein where the polymeric structure has a dielectric constant of from about 1.5 to 3.5.
According to still other embodiments of the present invention, methods of forming a polymeric structure having a plurality of cells therein include contacting a polymeric material comprising a copolymer having two or more phases with a composition comprising carbon dioxide and a chemical decomposition agent to remove at least one of the two or more phases from the polymeric material to form the polymeric structure having a plurality of cells therein. The copolymer includes a continuous first phase that comprises a first polymer chain, and a second phase that comprises a second polymer chain.
According to yet other embodiments of the present invention, methods of forming a polymeric structure having a plurality of cells therein where the plurality of cells have an average diameter of from about 1 to 25 nm are provided. The methods include contacting a polymeric material that includes a copolymer having two or more phases with a composition comprising carbon dioxide to remove at least one of the two or more phases form the polymeric structure having a plurality of cells therein where the plurality of cells have an average diameter of from about 1 to 25 nm. The copolymer includes a continuous first phase that comprises a first polymer chain, and a second phase that comprises a second polymer chain.
According to still other embodiments of the present invention, methods of forming a polymeric structure having a plurality of cells therein where the polymeric material has a dielectric constant of from about 1.5 to 3.5 include contacting a polymeric material that comprises a copolymer having two or more phases with a composition comprising carbon dioxide to remove at least one of the two or more phases from the polymeric material to form the polymeric structure having a plurality of cells therein, wherein the polymeric structure has a dielectric constant of from about 1.5 to 3.5. The copolymer includes a continuous first phase that comprises a first polymer chain, and a second phase that comprises a second polymer chain.
According to other embodiments of the present invention, methods of forming a polymeric film for use as a dielectric material in a microelectronic device are provided. The methods include contacting a polymeric material that comprises a copolymer having two or more phases with a composition comprising carbon dioxide to remove at least one of the two or more phases from the polymeric material to form the polymeric film for use as a dielectric material in a microelectronic device. The copolymer includes a continuous first phase that comprises a first polymer chain, and a second phase that comprises a second polymer chain.
According to still other embodiments of the present invention, methods of forming a polymeric film for use as a dielectric material in a microelectronic device include contacting a polymeric material comprising a first phase that includes a first polymer and a second phase that includes a second polymer with a composition comprising carbon dioxide to remove the second polymer from the polymeric material to form the polymeric film for use as a dielectric material in a microelectronic device.
According to yet other embodiments of the present invention, polymer structures include a polymeric matrix having a plurality of cells therein where the plurality of cells have an average diameter of from about 1 to 25 nm.
According to still other embodiments of the present invention, microelectronic devices include a dielectric material that comprises a polymeric matrix having a plurality of cells therein where the plurality of cells have an average diameter of from about 1 to 25 nm.